Polyepichlorohydrin aerosol gaskets

ABSTRACT

Solutions of polyepichlorohydrin can be lined in the gasket channel of aerosol mounting cups by conventional lining equipment to yield gaskets with gas retention properties superior to those of neoprene gaskets.

United States Patent [191 Gribens et al.

POLYEPICHLOROHYDRIN AEROSOL GASKETS Inventors: Joel A. Gribens,Framingham;

Gregory P. Cogliano, Canton. both of Mass.

Assignee: W. R. Grace & Co., Cambridge,

Mass.

Filed: July 25, 1974 Appl. No.: 491,748

Related U.S. Application Data Division of Ser. No. 413.654. Nov. 7.1973.

U.S. Cl. 220/81 R; 222/4021 Int. Cl B65d 7/34 Field of Search 260/2 A;264/268;

220/81 R; ZZZ/402.24. 402.1

References Cited UNITED STATES PATENTS 12/1948 Maeder et a1 264/268 X 1June 10, 1975 OTHER PUBLlCATlONS Maeda. "Characteristics of VariousSynthetic Rubbers. Chem. Abstracts 68, 105861p (1968).

Primary ExaminerMorris Liebman Assistant ExaminerE. A. Nielsen Attorney.Agent, or Firm-Armand McMillan; C. E. Parker 5 7 1 ABSTRACT So1utions ofpolyepichlorohydrin can be lined in the gasket channel of aerosolmounting cups by conventional lining equipment to yield gaskets with gasretention properties superior to those of neoprene gaskets 1 Claim, N0Drawings 1 POLYEPICHLOROHYDRIN AEROSOL GASKETS This is a division ofapplication Ser. No. 4l3,654, filed Nov. 7, 1973.

THE PRIOR ART Pressurized aerosol containers are widely used to packageand dispense an ever-increasing variety of materials. In thesecontainers, the product to be dispensed is confined under pressure bymeans of a volatile propellant and is discharged in a controlled mannerthrough a valve-actuated orifice.

A typical aerosol unit is composed of a hollow cylindrical containerclosed at one end and provided with an opening at its opposite end forreceiving a dispensing valve assembly. A metal mounting cup serves as aclosure for the container and also as a support for the valve assemblywhich is tightly fitted within an aperture centrally located in the cup.The mounting cup carries an annular gasket adapted at its outer edge tobe crimped to the walls forming the opening in the container and therebyform a seal upon crimping.

The gasketing material used in aerosol mounting cups must be elastic andresilient. It must be capable of yielding under deforming forces toestablish a satisfactory seal when the cup is crimped to the container.It must also be capable of maintaining the seal during normal storageperiods. Often selected for this function are gaskets prepared fromsolvent-based rubber compositions which comprise an elastomer dissolvedin a volatile organic solvent. The compositions may also containpigments, fillers, curing agents and other conventional compoundingingredients. To prepare gaskets from an elastomeric composition, a bandof the fluid composition is deposited in the annular channel of themounting cup while the cup is being rotated beneath a metering nozzlethrough which the composition flows to form a continuous annulardeposit. This deposit is subsequently converted into a dry solidelastomeric sealing mass by expulsion of the solvent and cure atelevated temperatures.

Because of superior resistance to oxidation and to oils and propellantsas well as to various other chemicals commonly found in aerosolcontainers, neoprene (a chlorobutadiene polymer) has become the favoredelastomer in this type of composition. Nevertheless, because of thegreat variety of materials and conditions encountered in aerosolpackaging, the quest for improved gasketing materials continues.

SUMMARY OF THE INVENTION It has now been discovered thatpolyepichlorohydrin compounds in solution form can be rapidly applied tothe gasket channel of aerosol can valve mounting cups to yield, afterdrying and curing, gaskets with superior gas retention properties.

DETAILED DESCRIPTION The compositions with which the benefits of thepresent invention can be obtained are solutions of polyepichlorohydrinelastomer in an organic liquid such as toluene. The polymer solutionsare prepared typically in the following manner:

POLYEPICHLOROHYDRIN COMPOUND The following chemicals, in the proportionslisted, are milled on a Banbury mixer for five minutes with thetemperature not exceeding 180F:

Ingredients Parts by Weight Polyepichlorohydrin rubber I000 Zincstearate l.0 Magnesium oxide 5.0 Carbon black 30.0 2-Mercaptoimidazolinel .5

The rubber compound thus obtained is then milled into a sheet, choppedand dissolved in toluene to yield a solution with a solids content ofabout 38 percent.

The rubber used for this compound is an amorphous epichlorohydrinhomopolymer having a molecular weight of about 5,000 in the raw state.Suitable elastomers of that type differ from other conventionalpolyepichlorohydrins in that they are neither low molecular liquids norhard crystalline materials. These usable elastomers are prepared, forexample, in an inert organic solvent at moderate temperatures (30 to C)in the presence of a small quantity of an organoaluminum catalystmodified according to the method described in U.S. Pat. No. 3,135,705.The polymer may contain a minor quantity of units derived from ethyleneoxide and the molecular weight may vary within the range of about 4,000to 20,000.

As to the rest of the ingredients formulated into the compound beingdescribed, they will be recognized as conventional rubber compoundingmaterials in the nature of fillers, plasticizers, curing agents and thelike. As such, it is contemplated that they may be omitted and replacedby equivalent conventional substances without unduly affecting theutility of the composition.

HIGH NEOPRENE COMPOUND A polychloroprene rubber content solution wasprepared according to Example 3 of U.S. Pat. No. 3,748,297. Theingredients employed were the following:

Ingredients Parts by Weight These ingredients were mixed and dissolvedin the conventional manner disclosed in U.S. Pat. No. 3,389,l l3,described below.

LOW NEOPRENE COMPOUND A compound was prepared according to the methoddescribed in Example 1 of U.S. Pat. No. 3,389,113:

Ingredients Parts by Weight Polychloroprene (Neoprene GN) I00 SodiumAcetate 1.5 Paraffin wax 2.0

Buca clay 99.8

to about 57% total solids by weight Toluene The polymer, paraffin wax,sodium acetate and about 80 parts of the clay were milled together on atwo-roll rubber mill. A blend containing the magnesium oxide and smallportions of dioctyl phthalate and zinc resinate solution were added tothe rubber mix. After a smooth working sheet was obtained, the batch wastransferred to an internal type mixer. Another blend containing thesilicon dioxide, zinc oxide, a small portion of plasticizer and theremaining zinc resinate solution was then added along with the peptizersand the remaining clay and plasticizer. After mixing was complete, thebatch was solvated in the toluene.

EXAMPLE 1 To test the rubber compounds just described and compare theirperformance as gaskets, the solutions were lined through a Dewey andAlmy electropneumatic nozzle into the gasket channel of a number ofaerosol mounting cups. The lined cups were then dried and curedaccording to the following standard laboratory schedule:

1 hour air dry 1 hour 155F I hour 200F 1 hour 325F except that in thecase of the polyepichlorohydrin compound, the last hour of treatment wasat 347F.

The resulting gaskets has the following dimensions and wet weight:

Thickness Wet film Weight Polyepichlorohydrin 0.016 inch 645 mg Highneoprene 0.020 600 mg Low neoprene 0.025 500 mg Crimping Condition DepthDiameter (inch) (inch) Polyepichlorohydrin (HYDRIN) 0.180 1.070 0.1701.060 Polychloroprene-high (PCHi) 0.210 1.070 0.200 1.060

Polychloroprene-low (PCLo) Each compound and each crimping condition wasthen tested against three different packs for leakage. The packs usedwere: (1) P12, difluorodichloromethane alone; (2) Pl2/EtOH, P12 andethyl alcohol; and (3) P11/P12/MeCl, P12 with trichlorofluoromethane andmethylene chloride.

The materials tested, the conditions and the results obtained aresummarized in the next table. The results are stated in terms of averageweight loss and number of can failures for each set of eight cans testedat the crimping and pack conditions indicated. The weight loss figuresare given in milligrams of fluid lost during a period of 52 weeks ofstorage at F. Failures are cans which either lost more than 5.5 g offluid during that storage period or were seen bubbling within sevenminutes of immersion in a F bath.

TABLE I (Eight Cans Per Condition] Average Depth Diameter Wt. Loss No.

Com- (inch) (inch) Pack (mg) Fail pound PCHi 0.210 1.070 P12/P11/MeCl2,768 3 HYDRlN 0.180 1.070 Pl2/Pl1/MeCl 518 0 PCLo 0.210 1.070Pl2/Pl1/MeCl 3,426 0 PCHi 0.210 1.070 P12/P11/MeC1 3,389 4 HYDRIN 0.1801.070 P12/P11/MeCl 621 0 PCLo 0.210 1.070 Pl 2/Pl l/MeCl 2,918 l PCHi0.200 1,060 P12/P1l/MeCl 653 0 HYDRIN 0.170 1.060 P1 2/P1 l/MeCl 980 0PCLo 0.200 1.060 P1 2/Pl l/MeCl 2,740 0 PCHi 0.200 1.060 P1 2/P1 l/MeCl851 0 HYDRIN 0.170 1.060 P1 2/P1 l/MeCl 704 0 PCLO 0.200 1.060 P] 2/Pll/MeCl 3,202 1 PCHi 0.210 1070 P1 ZIETOH 2,182 3 HYDRIN 0.180 1.070 P1ZIETOH 26 0 PCLo 0.210 1.070 Pl Z/ETOH 3,468 3 PCHi 0.210 1.070 P1ZIETOH 1,128 6 HYDRlN 0.180 1.070 P12/ETOH 56 0 PCLo 0.210 1.070 Pl2/ETOH 13,270 5 PCHi 0.200 1.060 P12/ETOH 0 HYDRIN 0.170 1.060 P1 2/ETOH40 0 PCLo 0.200 1.060 P12/ETOH 6,143 3 PCHi 0.200 1.060 P12/ETOH 307 0HYDRIN 0.170 1060 P1 2/ETOH 56 0 PCbo 0.200 1.060 P 2/ETOH 38,570 8 PCHi0.210 1.070 Pl 2 40,000 8 HYDRlN 0.180 1.070 Pl 2 148 0 PCbo 0.210 1.070Pl2 6,568 3 PCHi 0.210 1.070 pl 2 30,758 8 HYDRlN 0.180 1.070 P12 98 0PCLo 0.210 1.070 Pl2 6,352 4 PCHi 0.200 1.060 P l 2 2,424 3 HYDRIN 0.1701.060 P12 47 0 PCLo 0.200 1.060 P12 2,337 0 PCHi 0.200 1.060 P12 1,818 lHYDRIN 0.170 1.060 P12 68 O PCLo 0.200 1060 F12 4,695 2 OverallPropellant Can Failures Compound Losses (per 96 cans)Polyepichlorohydrin 280 mg 0 Polychloroprene-High Concentration 7,204 mg36 Polychloroprene-Low Concentration 7,807 mg 30 EXAMPLE 2 The effect offiller and plasticizer level on the gas retention performance ofpolyepichlorohydrin aerosol age 52-week propellant loss in milligramsshown by the nine cans in that unit. The second figure, that after thecomma, shows the number of cans that have failed, either by bubblingwithin seven minutes of immersion in gaskets was determined by preparingthe various com- 5 o positions shown in Table 11 and lining them in themana 1 F bath or by 105mg morcothan g propellant er already described inExample 1 1 within one year storage at 100 F. Data obtained under TABLE11 Epichlorohydrin 100.0 100.0 100.0 100.0 100.0 100.0

Zinc Stearate 1.0 1.0 1.0 1.0 1.0 1.0

Magnesium Oxide 5.0 5.0 5.0 5.0 5.0 5.0

Calcium Carbonate 50.0 50.0 100.0 200.0 50.0 50.0

Dioctyl Phthalate 0 0 0 15.0 30.0

Z-Mercaptoimidazoline 1.5 1.5 1.5 1.5 1.5 1.5

Azelaic Acid 0 2.0 2.0 2.0 2.0 2.0

Gaskets made from these compositions tested under the twelve crimp andpack listed in Table 111:

low concentration composition (PCLo) are included for comparisonpurposes.

TABLE IV (KEY: 417?, 3 Average Weight boss 4177 mg; 3 Failing Cans)COMPOUND Test Condition PCLo No. 1 No. 2 No. 3 No. 4 No. 5 No. 6

l 245, 0 114, 0 206,0 242, 0 285, 0 315,0 253, 0 11 4177, 3 4122, 3 548,1 4119, 3 3510, 3 469 1 24,0 111 911, 1 505, 1 239, 2 1865, 2 407, 130,0 486, 2 IV 387, 0 174, 0 340, 0 258, 0 256, 0 398,0 367,0 V 416, l4124, 3 423, 1 35, 0 975, 2 35, 0 480, 3 V1 1870, 2 64, l 431, 2 713, 22336, 3 75, 0 1875, 2 V11 254, 0 485, 0 195, 0 156, 0 203, 0 204, 0 178,0 V111 74, 0 501, 1 369, 1 1020, 2 503, 1 500, 1 353, 1 IX 2083, 2 98,093, 0 530, 1 120, l 97, 0 82, 0 X 625, 0 202, 0 333, 0 228, 0 232,0 308,0 267, 0 X1 711, 1 86, 0 7297, 4 1773, 2 7686, 6 483, 1 504, 1 X1125665. 9 908, 2 51, 2 606, l 4202, 5 150, 0 428, 1 Average Loss 2943 949877 963 1727 256 442 No. Fail/ Total Cans 19/108 1 H108 13/108 22/10822/108 3/108 /108 TABLE 111 Again, on comparison of the sixpolyepichlorohydrin compositions to polychloroprene, the performance ofI oe th Diameter the gaskets of the invention as summarized by the aver-Condmo" Pack age loss for all conditions and by the total of can fail- IP12/P1 Men 0200 1,070 ures is clearly demonstrated except in the casewhere 11 P 2/ O 0.200 1070 an extremely high level of filler is used(compositions 111 P12 0.200 1.070 1V P12/Pl l/MeCl 0.200 1.060 VP12/ETOH 0%00 1.060 It also becomes apparent that variations in thenature 5:3, HMBC, 8:788 and level of ingredients of the gasketingformula of the V111 P12/ETOH i 0.190 1.070 mventton can be carried outby the man skilled in the IX P12 0.190 1.070 X P12/PI Mac! (H90 [060 artw thout departmg from the scope of the invention x1 PIZ/ETOH 0.190 1.060as Claimedx|1 P12 0.190 1.060 w we claim (,0 1. An aerosol canvalve-mounting cup equipped with an annular gasket which has beendeposited into the annular channel of the cup in the form of a solutionof an amorphous polyepichlorohydrin elastomer having a molecular weightwithin the range of about 4,000 to about 20,000, the solution havingbeen subsequently dried and the dry elastomer cured in situ at elevatedtemperature.

1. AN AEROSOL CAN VALVE-MOUNTING CUP EQUIPPED WITH AN ANNULAR GASKETWHICH HAS BEED DEPOSITED INTO THE ANNULAR CHANNEL OF THE CUP IN THE FORMOF A SOLUTION OF AN AMORPHOUS POLYEPICHLOROHYDRIN ELASTOMER HAVING AMOLECULAR WEIGHT WITHIN THE RANGE OF ABOUT 4,000 TO AOUT 20,000, THESOLUTION HAVING BEEN SUBSEQUENTLY DRIED AND THE DRY ELASTOMER CURED INSITU AT ELEVATED TEMPERATURE.